Storage tube system and method



Oct. 4, 1966 R. G.WILLIAMS ETAL 3,277,333

STORAGE TUBE SYSTEM AND METHOD Filed Dec. 13, 1963 26%37 *Iil 25- 5 S E '3 I A I2 5 Q E l5 E Q B I6 ,E E

-TIMER TFj VERT. SWEEP NON STORE 73 5s AMP AMP. NON-STORE STORE 74 I 591 INPUT INPUT NON-STORAGE STORAGE IN FORMATION INFORMATION POSITIONS OF :ELE-

TIMER 79 NON I RE STORED STORED I NON- Ill NON- L I STORE STORED STORED T|MEI= INVENTORS A 4 I q ATTORNEYS United States Patent 3,277,333 STORAGE TUBE SYSTEM AND METHOD Robert G. Williams, Michael F. Toohig, and Roger W.

Hunter, Fort Wayne, lind., assignors to International Telephone and Telegraph Corporation, Nutley, N.J., a

corporation of Maryland Filed Dec. 13, 1963, Ser. No. 330,288 25 Claims. (Cl. 31512) This invention relates generally to direct viewing storage tube systems and methods of operating such storage tubes, and more particularly to a system and method for simultaneously presenting both stored and non-stored information in direct viewing storage tubes.

A conventional type of direct viewing storage tube in corporates a display screen, an aperture-d charge storage electrode having a conductive backing member with insulating material having secondary emissive properties deposited thereon, an electron gun for forming and directing a pencil electron beam toward the storage electrode and display screen, and another electron gun for forming and directing a low velocity flood electron beam toward the storage electrode and display screen. In the conventional mode of operation of such a storage cathode ray tube, the high velocity pencil beam, modulated by input signal information to be stored and displayed, is scanned over the storage electrode thereby providing a charge pattern thereon in accordance with the input signal information. The low velocity flood electron beam passes through the apertures in the storage electrode to the display screen, being modulated by the incremental charges on the storage electrode which form the charge pattern, thereby to display a visible image corresponding to the charge pattern.

There are applications for direct viewing storage tubes in which it is desirable to display non-stored information, i.e., television-type information superimposed upon stored information, such as radar data. Two techniques have been employed to provide both stored and non-stored writing in direct viewing storage tubes. In the first of these, a storage electrode is provided incorporating a dualeffects insulator, i.e., one which is capable of high secondary emission yields and also of high bombardment-induced-conductivity. In such tubes, during non-stored writing, the operating potential of the electron gun employed for write-through is adjusted so that the bombardmentinduced-conductivity and secondary emission currents are equal and opposite; such a tube and method is described in Patent No. 3,086,139 to N. H. Lehrer. In such tubes, however, the display of non-stored information may not be sufliciently bright. Bombardment-induced-conductiviity is related to beam current density and thus when sufiicient beam current is provided for satisfactory brightness, the bombardment-induced'conductivity current predominates and erasure of the charge pattern or writing results, depending upon the polarity of the conductive backing member. Furthermore, bombardment-induced-conductivity gain at any point on the insulator depends upon the potential gradient across insulator at that point and thus, even though bombardment-induced-conductivity currents and secondary emission yields may be balanced for any incremental area of the insulator, they may not be balanced at another incremental area at which the potential gradient is different, and therefore writing or erasing will result depending upon the gradient at any point. Thus, tubes of the type employing a dual effects insulator are not capable of true non-stored writing since some stored writing and/or charge erasure does occur because of the inherent characteristics of the dual-effects insulator.

In the second type of system for obtaining simultaneous display of stored and non-stored information, which is described in Patent No. 2,981,863 to Robert J. Schneeberger and John G. Castle, Jr., the electron gun employed for non-stored writing or write-through is operated to provide beam energy equal to the second cross-over potential of the insulator which represents an equilibrium condition between primary and secondary electrons. The second cross-over point varies however, from one incremental area to another on the insulator and thus, the electron beam energy will be below the second cross-over point at one incremental area and above at another, again providing some charge writing and/ or charge erasure.

It is therefore desirable to provide a direct viewing storag tube system and method for simultaneously displaying both stored and non-stored information which provides improved brightness of the non-stored information, prevents destruction, i.e., erasure of the stored information, prevents storage of the temporary, i.e., non-stored information, and which may be applied to existing tubes.

It is accordingly an object of the invention to provide an improved direct viewing storage tube system and method for simultaneously displaying stored and non-stored information.

Another object of the invention is to provide an improved direct viewing storage tube system and method for simultaneously displaying stored and non-stored information in which erasure of stored information and storing of non-stored information is prevented A further object of the invention is to provide an improved direct viewing storage tube system and method for simultaneously displaying stored and non-stored information which is applicable to existing tubes.

In accordance with the broader aspects of the invention, a high velocity pencil writing beam is provided which writes a charge pattern onto a conventional storage electrode in accordance with the beam modulation. A low velocity flood electron beam is provided which passes through the apertures in the storage electrode to the display screen, being modulated by the charge pattern to provide a visible image corresponding to the charge pattern. Writing or write-through of temporary or nonstored information is accomplished by providing a low velocity pencil electron beam which approaches the storage electrode at substantially zero energy. This low velocity pencil beam which is modulated by the nonstored information input thus passes through the apertures in the storage electrode to the display screen to display the non-stored information without impact upon the storage electrode and therefore without erasing the previously stored charge pattern or storing a new charge pattern thereon.

The above-mentioned and other features and objects of this invention and the manner of attaining them will become more apparent and the invention itself will be best understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic diagram illustrating the system and method of the invention; and

FIG. 2 is a diagram illustrating the pulsing cycle employed in the system of FIG. 1.

Referring now to FIG. 1, there is shown at 10 a conventional form of direct viewing charge storag tube comprising an evacuated envelope 11 having a faceplate portion 12, an enlarged portion 13 and a neck portion 14. A conventional phosphor display screen 15 is deposited upon the inner surface of the faceplate portion 12 and has an aluminum coating 16 deposited thereon, as is Well known to those skilled in the art. A writing electron gun 17 is positioned in the neck portion 14 and comprises cathode 18, control grid 19, and other focusing coils and acceleratforming and directing a pencil electron beam toward the ing ClBOiI'OdGS including conductive wall coating 20 for display screen 15, as is well known to those skilled in the art. Suitable beam deflection means, such as horizontal and vertical deflection yokes 22 and 23 are provided.

A conventional charge storage electrode 24 is provided having a plurality of apertures 25 therein, charge storage electrode 24 comprising a metal backing member 26 facing the display screen 15 with insulating material 27 deposited thereon and facing the electron gun 17, insulating material 27 having secondary emissive properties. A conventional collector electrode 28 is provided within the envelope 11 spaced between the storage electrode 24 and the gun 17, as shown.

A flood electron gun 29 is provided coaxial with the writing electron gun 17 and comprises an anode 30 and a cathode 32; flood gun 29 may be the type more fully described and illustrated in Patent No. 2,864,020 to Paul Rudnick ad Michael F. Toohig, and assigned to the assignee of the present application. Conductive coatings 33, 34 and 35 are formed on the inner wall of enlarged portion 13 of envelope 11 and serve as collimating electrodes as will hereinafter be more fully described.

In both modes of operation of the system and method of the invention, i.e., both stored and non-stored writing, collimating electrodes 33 and 35, wall coating 20 and cathode 18 are coupled to the terminals 36, 37, 38 and 39 of suitable sources of fixed potential; in a specific em-, bodiment, sources 36 and 37 to which collimating electrodes 33 and 35 are respectively coupled may be +60 volts and +20 volts, source 38 to which wall coating 20 is coupled may be +3 volts and source 39 to which cathode 18 is coupled may be +1500 volts. Anode 30 of flood gun 29 is also coupled to terminal 40 of a fixed source of potential which in the specific embodiment may be +20 volts.

In the conventional storage mode of operation, i.e., the writing and display of stored information, aluminum coating 16 is coupled by switch 42 to terminal 43 of a source, which may be +6000 volts in the specific embodiment, and backing member 26 of storage electrode 24 coupled by switch 44 to terminal 45 of a source, which may be +10 volts. The insulator 27 is assumed to initially be at a potential of about 3 volts after being erased by the normal means of pulsing the backing electrode 26, such as described in US. Patent No. 3,124,717 to G. W. King et al., column 3, lines 36-40, thereof. Collector electrode 28 is coupled by switch 46 to terminal 47 of a source which may be +160 volts and the center collimating electrode 34 is coupled to switch 48 to terminal 49 of a source, which may be +30 volts. Cathode 32 of flood gun 29 is coupled by switch 50 to terminal 51 of a source, which may be at ground potential in the specific embodiment and horizontal and vertical deflection yokes 22, 23 are respectively coupled by switches 53 and 54 to suitable sweep generators 55 and 56, which in the illustrated embodiment provide faster scanning at a rate of 53,000 inches per second. Control grid 19 is coupled by switch 57 to amplifier 58 which has its input circuit 59 coupled to receive the signal information to be stored and which, in the specific embodiment, provides a grid drive of 15 volts. With switches 42, 44, 46, 48, 50, 53, 54 and 57 positioned as shown in FIG. 1 and respectively applying potentials, as indicated, a high velocity pencil electron beam, modulated by the signal information to be stored applied to input circuit 59 of amplifier 58, will be directed by writing gun 17 toward display screen 15 and scanned over insulator 27 of storage electrode 24 by deflection yokes 22, 23 and sweep generators 55, 56. This scanning of the modulated high velocity pencil electron beam over the insulator 27 will, by secondary emission, provide a charge pattern on the insulator corresponding to the signal to be stored. Flood gun 29 directs a low velocity electron beam toward display screen 15 which passes through the apertures 25 in the storage electrode 24, being modulated by the incremental charges on the insulator 27 which form the charge pattern, thereby to provide a visible image on the display screen 15 corresponding to the charge pattern. In this mode of operation and with the above-recited potentials applied, collimating electrodes 33, 34 and 35 collimate the flood beam so that it approaches the storage electrode 24 with normal incidence, as more fully described in Patent No. 2,917,658 to Roger W. Hunter and assigned to the assignee of the present application.

In the non-stored or write-through mode of operation of the system of FIG. 1, the backing member 26 of the storage electrode 24 is pulsed negative by an amount equal to the potential of the writing gun cathode 18 so that the writing gun pencil beam electrons approach the surface of insulator 27 with substantially zero energy. Thus, switch 44 is moved to its second position 60 to couple backing member 26 of storage electrode 24, through switches 62 and 63, the function of which will be hereinafter described, to terminal 64 of a source of potential, which in the specific embodiment, may be 1490 volts; it will be seen that the difference between the +10 volts applied to the backing member 26 during the storage mode and the 1490 volts applied during the write-through mode is 1500 volts i.e., the absolute potential of the cathode 18.

In the write-through mode, switch 46 is moved to its second position 65 to couple the collector of electrode 28 to terminal 66 of a source of potential which in the specific embodiment may be +670 volts and switch 48 is moved to its second position 67 to couple the center collimating electrode 34 to terminal 68 of a source of potential equal to that applied to the collector electrode 28 but of opposite sign, in this case -670 volts. The flood beam is terminated during the Write-through mode of operation by moving switch 50 to its second position 69 thereby to couple cathode 32 to terminal 70 of a source which, in the specific embodiment may be volts. Finally, switch 57 is moved to its second position 72 to couple control grid 19 of-writing gun 17 to amplifier 73 which has its input circuit 74 coupled to the source of non-storage signal information. It will be readily apparent that in the specific system described and illustrated, time sharing of the writing gun 17 is employed, i.e., writing gun 17 is used for writing both the stored and nonstored information, however, it will be readily understood that separate guns may be employed.

If during the write-through mode of operation the same potentials were applied to the collimating electrodes 33, 34 and 35 as were applied during the storage mode for collimating the flood beam, the low 'velocity pencil beam would not be properly collimated particularly adjacent the outer edges of the storage electrode 24, which would result in a nonuniform display on display screen 15 due to lack of normality of approach of the low velocity electron beam. Modification of the potentials applied to the collector electrode 28 and to the collimating electrodes 33, 34 and 35 during the write-through mode of operation, as above described, provides a strong lens system to collimate the low velocity pencil beam so that it approaches the storage electrode 24 with normal incidence.

We have found that during the write-through mode of operation, brightness of the non-stored information display may be increased by increasing the writing gun grid drive. For this reason, amplifier 73 which couples the control grid 19 of writing gun 17 to the source of nonstored information may, in a specific embodiment, provide a grid drive of 25 volts. We have further found that brightness of the non-stored display is increased significantly by reducing the scanning rates, i.e., increasing the dwell time of the low velocity pencil beam. For this reason, in the write-through mode, switches 53, 54 may be moved to their second positions 75, 76 respectively to couple the deflection yokes 22, 23 to horizontal and vertical sweep generators 77, 78 which, in the specific embodiment, provide a scanning rate of 20,000 inches per second.

It will now be readily seen that the stored and nonstored information are not instantaneously simultaneously written on display screen 15, but on the contrary in the time-sharing mode of operation described, are alternately written. Thus, in order that the two images may appear to the viewer to be superimposed one upon the other, it is necessary that the system be switched or pulse cyclically between the storage and the write-through modes at a sufliciently high rate to avoid flicker. Thus, switches 44, 46, 48, 5t 53, 54, and 57 are ganged, as indicated by the dashed line 91 and operated by a suitable timer 79. It is Well known that a repetition rate of 60 cycles per second is sutficiently rapid to avoid flicker.

Referring to FIG. 2, the relative degrees of apparent brightness of the stored and non-stored displays depends upon the relative numbers of the stored and non-stored timing pulses per cycle (referring to the 60 cycle repetition rate). Since the brightness of the stored information is a function of the on time of the flood beam, which floods the entire area of the storage electrode 24 and the display screen 15, whereas the brightness of the non-stored display is a function of the on time of the low velocity pencil beam which is scanned over the storage electrode and the display screen, it will be seen that equal brightness of the two images will be provided with a much shorter storage interval than non-storage interval. However, it may be desirable to provide a contrast between the brightness of the stored and non-stored displays in order to distinguish between the two types of information and we have found that a suitable contrast is provided by having the non-storage pulses provided by timer 7?, i.e., with the switches actuated to their second positions, about /3 of each switching cycle and the storage intervals about /3, these respective non-stored and stored intervals providing, in the specific embodiment, relative brightness of the non-stored and stored displays of 200 foot lamberts and 800 foot lamberts respectively. For equal brightness, the non-stored intervals would be about of each cycle.

The above described system also lends itself to selective erasure of stored information and also to the provision of an electrical output signal in accordance with the stored information. Selective erasure may be accompiished in the specific embodiment with the switches 44, 46, 4t 5t}, 53, 54 and 57 in their second, i.e., writethrough positions, to couple the backing member 26 of the storage electrode 24 to a terminal 82 of a source of potential slightly more positive than the source 64, for example, 1480 volts in this specific embodiment. Thus, with all of the other potentials being the same as in the write-through mode of operation, the low velocity electron beam provided by the writing gun 17 will impinge upon the insulator 27 of the storage electrode 24 to provide erasure of the charge pattern in a manner substantially identical to that provided in normal flood gun erasure. it will be readily seen that selective erasure of any desired area of the storage electrode may be accomplished by suitable timing of the actuation of switch 63 or by conventional techniques such as pulsing the cathode It; or grid 19. Thus, a single spot of any desired size and in any location upon the storage electrode 24 can be selectively erased without erasing the charge pattern on remaining areas of the storage electrode.

Electrical read-out of the stored information may also be accomplished by moving switches 42, and 62, which may be ganged as shown by the dashed line 83, to their second positions 84 and 90 respectively, with the remaining switches 44, 46, 48, 5t), 53, 54 and 57 remaining in their write-through positions. Moving switch 42 to its second position 84 couples the aluminum coating 16 upon the display screen 15 to terminal 85 of a source of potential substantially lower than that provided for visual display, such as +200 volts in the specific embodiment. A suitable load resistor 86 is provided in series between terminal 85 and switch position 84 and an output circuit 87 as coupled by coupling capacitor 88 to the switch position 84 in conventional fashion.

Switch 62 in its second position couples the backing member 26 of the storage electrode 24 to a terminal 89 of a source of potential slightly more negative than that applied to backing member 26 during normal writethrough operation such as 1491 volts, all other potentials remaining the same as during the normal writethrough mode of operation. With these potentials applied, the low velocity writing beam provided by the writing gun i7 is modulated by the charge pattern on the storage electrode 24 and provides an electrical output signal across resistance 86 in accordance with the charge pattern. It will be readily seen that this electrical output signal could also be taken off of the collector electrode 28, however, better results are obtained by taking it from the display screen. it will be readily apparent that with this much lower potential applied to the display screen, no image will appear thereon since the beam energy is too low to excite the phosphor.

It will be understood that an electrical output signal is present when the phosphor is operated at high voltage during both of the display modes, i.e., storage and writethrough, however, this signal is so small in comparison with the high voltage applied to the phosphor, that it is diflicult to detect and extract.

It will now be seen that there is provided in accordance with the invention a system and method for presenting non-stored information in direct viewing storage tubes in which no modification, i.e., either erasure or addition, to the previously stored information takes place because of the negative grid characteristics of the backing member of the storage electrode during the write-through mode of operation. The system and method of this invention is therefore completely independent of insulator characteristics. Furthermore, since the non-stored writing gun beam does not land on the insulator, brighter non-stored displays are obtainable since writing beam currents may be increased over the low values necessarily employed when relying upon bombardment-induced-conductivity and secondary emission effects. It will further be readily seen that the system and method of the invention is readily applicable to existing direct viewing storage tubes. While the system has been described and illustrated as embodied in a storage tube having axial symmetry, i.e., having coaxial write and flood guns, it will be readily apparent that it may be embodied in tubes having an offaxis writing gun by the addition of conventional circuitry to correct for deflection aberrations.

While we have described above the principles of our invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of our invention.

What is claimed is:

1. In a direct viewing storage tube system: display screen means; apertured charge storage electrode means having a conductive backing member and a secondary emissive insulator thereon; means for at first times directing a high velocity pencil electron beam onto said storage electrode means thereby to provide a charge on an elemental area thereof responsive to the beam current, said means for directing said high velocity beam including cathode means; means for directing a low velocity flood beam of electrons onto said storage electrode means which passes through the apertures therein and is modulated by the elemental charges thereon; means applying first potentials to said display screen means, said backing member, said cathode means, and said flood beam means; means for at other times directing a low velocity pencil beam onto said storage electrode means which approaches the same at substantially zero energy, said means for directing a low velocity pencil beam including means applying a different potential to one of said backing member and cathode means; and means for modulating said high and low velocity pencil beams and for scanning the same over said storage electrode means whereby stored information is displayed on said display screen during said first times and non-stored information is displayed during said other times.

2. A direct viewing storage tube system for simultaneously displaying stored and non-stored information comprising: a direct viewing storage cathode ray tube including display screen means, means for directing at least one pencil electron beam toward said display screen means and including cathode means, beam scanning means and beam modulating means, means for directing a flood electron beam toward said display screen, and apertured storage electrode means having a conductive backing member and insulator material having secondary electron emissive properties on said backing member; means for applying first potentials to said display screen means, said backing member, said cathode means and said flood beam directing means thereby to scan a modulated high velocity pencil electron beam over said storage electrode means for providing a change pattern thereon in accordance with said modulation and to direct a low velocity flood electron beam onto said storage electrode means which passes through the apertures therein being modulated by the charges thereon whereby stored information is displayed on said display screen means, the potential of said backing member being substantially more positive than that of said cathode means and substantially less positive than that of said display screen means; and means for at times applying a different potential to one of said backing member and cathode means thereby to scan a modulated low velocity pencil beam over said storage electrode means which approaches the same at substantially Zero energy whereby non-stored information is displayed on said display screen means, the potential of said backing member approaching that of said cathode means and being substantially less positive than that of said display screen means.

3. The system of claim 2 wherein said tube includes collimating electrode means, wherein said means for applying first potentials includes means for applying first potentials to said collimating electrode means for collimating said flood electron beam, and wherein said means for applying a different potential includes means for applying different potentials during said times to said collimating electrode means for collimating said low velocity pencil beam.

4. The system of claim 3 wherein said means for applying a different potential includes means for terminating said flood electron beam during said times.

5. The system of claim 2 wherein said means for applying a different potential applies a different potential to said backing member, said different potential differing from the first potential applied to said backing member by an amount substantially equal to the potential applied to said cathode means.

6. The system of claim 2 further comprising means for cyclically actuating said means for applying a different potential at a predetermined repetition rate to permit simultaneous viewing of said stored and non-stored information.

7. The system of claim 2 further comprising an electrical signal output circuit coupled to said display screen means, and means for applying a different potential to said display screen means during said times which is substantially less positive than said first potential applied to said display screen means and more positive than said backing member whereby said low velocity pencil beam is modulated by the charges on said storage electrode means to provide an electrical output signal in said output circuit in accordance with said stored information.

8. The system of claim 3 wherein said means for applying a different potential applies a first different potential to said backing member during said times which differs from the first potential applied to said backing member by an amount substantially equal to the potential applied to said cathode means thereby to provide said display of non-stored information, and further comprising means for selectively applying a second different potential to said backing member during said times which is slightly more positive with respect to the potential of said cathode means than said first named different potential whereby said low velocity pencil beam impinges upon said storage electrode means selectively to erase the charges thereon.

9. The system of claim 3 wherein said means for applying a different potential applies a first different potential to said backing member during said times which differs from the first potential applied to said backing member by an amount substantially equal to the potential applied to said cathode means thereby to provide said display of non-stored information; and further comprising an electrical signal output circuit coupled to said display screen means, means for selectively applying a different potential to said display screen means during said times which is substantially less positive than said first potential applied to said display screen means and more positive than said backing member, and means for selectively applying a second different potential to said backing plate member during said times which is slightly less positive with respect to the potential of said cathode means than said first different potential whereby said low velocity pencil beam is modulated by the charges on said storage electrode means to provide an electrical output signal in said output circuit in accordance with said stored information.

10. A direct viewing storage tube system for simul taneously displaying stored and non-stored information comprising: a direct viewing storage cathode ray tube including a display screen; a first electron gun including a cathode for forming and directing a pencil electron beam toward said display screen and means for modulating said pencil beam in accordance with signal information, a second electron gun including means for forming and directing a low velocity flood electron beam toward said display screen, a storage electrode between said display screen and said electron guns having a plurality of apertures formed therein and comprising a metal backing member facing said display screen and insulating material having secondary electron ernissive properties on said backing member and facing said electron guns, a collector electrode spaced from said storage electrode on the side thereof toward said guns, collimating electrode means between said collector electrode and said guns, and means for scanning said pencil beam over said storage electrode; means for applying predetermined potentials to said cathode and said display screen such that said cathode is highly negative with respect to said display screen; and switching means having first and second positions, said switching means in said first position thereof applying first predetermined potentials to said backing member, collector electrode and collimating electrode means such that said backing member is substantially more positive than said cathode and said collector electrode is more positive than said backing member so that said pencil beam approaches said storage electrode at high velocity thereby providing a charge pattern thereon in accordance with the modulation of said beam and said flood beam passes through the apertures in said storage electrode being modulated by the charge pattern thereon thereby to display stored information on said display screen, the first potentials applied to said collector electrode and collimating electrode means being such that said flood beam is collimated to approach said storage electrode with normal incidence; said switching means in said second position thereof applying second predetermined potentials to said backing member, collector electrode and collimating electrode such that the potential of said backing member is changed toward that of said cathode by an amount substantially equal to the potential applied to said cathode so that said pencil beam approaches said storage electrode at substantially zero energy thereby passing through the apertures therein to display nonstored information on said display screen, the second potentials applied to said collector electrode and collimating electrode means being such that said low velocity pencil beam is collimated to approach said storage electrode with normal incidence; said switching means in said second position thereof disabling said second electron gun thereby to terminate said fiood electron beam.

11. The system of claim wherein said second gun is coaxial with said first gun, wherein said collimating electrode means comprises first, second, and third collimating electrodes sequentially spaced from said collector electrode to said guns, wherein said switching means in said first position thereof applies said first potentials to said collimating electrodes which are progressively less positive with respect to the potential of said collector electrode thereby to provide an electron lens for collimating said flood beam; and wherein said switching means in said second position thereof applies said second potential to said collector electrode which is positive and substantially higher than the first potential applied thereto and applies said second potential to said second collimating electrode which is negative and substantially equal to said second potential applied to said collector electrode thereby providing a strong lens for collimating said low velocity pencil beam.

12. The system of claim 10 further comprising means for rapidly actuating said switching means between said first and second positions thereof at a predetermined repetition rate, said switching means in said first position thereof coupling said modulating means to a source of signal information to be stored and in said second position thereof coupling said modulating means to a source of non-stored signal information to permit simultaneous viewing thereof.

13. The system of claim 10 wherein said switching means in said first position thereof couples said scanning means to sweep voltage generating means having a first predetermined frequency, said switching means in said second position thereof coupling said scanning means to sweep voltage generating means having a second predetermined frequency lower than said first frequency.

14. The system of claim it wherein said switching means in said first position thereof couples said modulating means to amplifying means having a first predetermined gain, said switching means in said second position thereof coupling said modulating means to amplifying means having a second predetermined gain higher than said first gain.

15. The system of claim 10 further comprising second switching means coupled to said backing member in said second position of said first-named switching means and having first and second positions, said second switching means in said first position thereof applying said second predetermined potential to said backing member, said second switching means in said second position thereof applying a third predetermined potential to said backing member which is slightly more positive with respect to the potential of said cathode than said second potential whereby said low velocity pencil beam impinges upon said storage insulating material thereby selectively to erase the charges thereon.

lid. The system of claim 10 further comprising second switching means coupled to said backing member in said second position of said first-named switching means and having first and second positions, said second switching eans in said first position thereof applying said second predetermined potential to said backing member, said second switching means in said second position thereof applying a third predetermined potential to said backing member which is slightly less positive with respect to the potential of said cathode than said second potential; and third switching means having first and second positions, said third switching means in said first position thereof coupling said display screen to said first named predetermined potential, said third switching means in said second position thereof coupling said display screen to an electrical signal output circuit and to a different potential which is substantially less positive than said first named potential applied to said display screen and more positive than said backing member whereby with all of said switching means in said second positions thereof said low velocity pencil beam is modulated by the charges on said insulating material to provide an electrical output signal in said output circuit in accordance with said stored information.

17. The method of simultaneously displaying stored and non-stored information in a direct viewing storage tube having display screen means and apertured charge storage electrode means comprising the steps of: writing a charge pattern onto said storage electrode with a high velocity pencil electron beam modulated in accordance with information to be stored; flooding said storage electrode with a low velocity flood beam which passes through said apertures in said storage electrode being modulated by the charge pattern thereon thereby to display said stored information on said display screen; and directing a pencil electron beam modulated in accordance with non-stored information toward said storage electrode which aproaches the same at substantially zero energy thereby passing through said apertures without impact on said storage electrode to display said non-stored information on said display screen.

18. The method of simultaneously displaying stored and non-stored information in a direct viewing storage tube having display screen means, apertured charge storage electrode means having a conductive backing member with insulating material having secondary emissive properties thereon, first electron gun means for providing a pencil electron beam and including a cathode, and second electron gun means for providing a low velocity flood electron beam, said method comprising the steps of: applying predetermined first potentials to said backing member and cathode to provide a high velocity pencil electron beam; modulating said high velocity pencil beam with information to be stored; scanning the modulated high velocity pencil beam over said storage electrode to write a charge pattern thereon in accordance with the modulation of said beam; directing said flood beam onto said storage electrode so that said flood beam passes through the apertures in said storage electrode means to said display screen means being modulated by said charge pattern thereby to display said stored information on said display screen means; applying a predetermined second potential to said backing member which approaches that of said cathode and which differs from the first potential applied to said backing member by substantially the potential applied to said cathode to provide a low velocity pencil electron beam which approaches said storage electrode means with substantially Zero energy; modulating said low velocity pencil beam with non-stored information; and scanning the modulated low velocity pencil beam over said storage electrode means so that said low velocity pencil beam passes through said apertures without impact on said storage electrode means to display said non-stored information on said display screen means.

19. The method of simultaneously displaying stored and non-stored information in a direct viewing storage tube having display screen means, apertured charge storage electrode means having a conductive backing member with insulating material having secondary emissive properties thereon, first electron gun means for providing a pencil electron beam and including a cathode, second electron gun means for providing a low velocity flood electron beam, and electron beam collimating electrode means between said storage electrode means and said gun beams, said method comprising the steps of: applying predetermined potentials to said display screen means and said cathode means; applying during first times a first predetermined potential level to said backing member substantially more positive than that of said cathode and less positive than that of said display screen means to provide a high velocity pencil electron beam; modulating said high velocity pencil beam with information to be stored; scanning the modulated high velocity pencil beam over said storage elecrtode means to write a charge pattern thereon in accordance with the modulation of said beam; during said first times directing said flood beam onto said storage electrode means so that said flood beam passes through said apertures in said storage electrode means to said display screen means being modulated by said charge pattern thereby to display said stored information on said display screen means; during said first times applying first predetermined potential levels to said collimating electrode means to cause said flood beam to approach said storage edectrode means with normal incidence; applying during second times a second predetermined potential level to said backing member which is more negative than the first potential level applied to said backing member by substantially the potential applied to said cathode to provide a low velocity pencil electron beam which approaches said storage electrode means with substantially zero energy; modulating said low velocity pencil beam with non-stored information; scanning the modulated low velocity pencil beam over said storage electrode means so that said low velocity pencil beam passes through said apertures without impact on said storage electrode to display said non-stored information on said display screen means; terminating said flood beam during said second times; and during said second times applying second predetermined potential levels to said collimating electrode means to cause said low velocity pencil beam to approach said storage electrode means with normal incidence.

20. The method of claim 19 comprising the further steps of scanning said high velocity beam at a first predetermined rate during said first periods, and scanning said low velocity beam at a second predetermined rate lower than said first rate during said second periods.

21. The method of claim 19 comprising the further steps of applying a signal having a first level to modulate said high velocity pencil beam during said first periods, and applying a signal having a second level higher than said first level to modulate said low velocity pencil beam during said second periods.

22. The method of claim 19 comprising the further step of pulsing said potentials applied to said backing member and said collimating electrode means between said first and second levels thereof at a predetermined rate to permit simultaneous viewing of said stored and non-stored information.

23. The method of simultaneously displaying stored and non-stored information in a direct viewing storage tube having a display screen, an apertured charge storage electrode having a conductive backing member with insulating material having secondary emissive properties thereon, first electron gun means for providing a pencil electron beam and including a cathode, second electron gun means coaxial with said first gun means for providing a low velocity flood electron beam, a collector electrode between said storage electrode and said guns, and three electron beam collimating electrodes spaced sequentially between said collector electrode and said guns, said method comprising the steps of: applying predetermined fixed potential levels to said display screen means and said cathode means; applying during first times a first predetermined potential level to said backing member substantially more positive than that of said cathode and less positive than that of said display screen means to provide a high velocity pencil electron beam; modulating said high velocity pencil beam with information to be stored; scanning the modulated high velocity pencil beam over said storage electrode to write a charge pattern thereon in accordance with the modulations of said beam; during said first times directing said flood beam onto said storage electrode so that said flood beam passes through said apertures in said storage electrode means to said display screen means being modulated by said charge pattern thereby to display said stored information on said display screen; during said first times applying a first predetermined potential level to said collector electrode which is more positive than said first potential level applied to said backing member; during said first times applying to said collimating electrodes first potential levels which are successively less positive than that of said collector electrode but all of which are more positive than said backing member thereby to collimate said flood beam; applying during second times a second predetermined potential level to said backing member which is more negative than the first potential level applied to said backing member by substantially the potential level applied to said cathode means and which approaches the potential level of said cathode means to provide a low velocity pencil electron beam which approaches said storage electrode with subtantially zero energy; modulating said low velocity pencil beam with non-stored information; scanning the modulated low velocity pencil beam over said storage electrode so that said low velocity pencil beam passes through said apertures without impact on said storage electrode to display said non-stored information on said display screen; terminating said flood beam during said second times; during said second times applying a second predetermined positive potential level to said collector electrode which is substantially more positive than the first potential level applied thereto; and during said second times applying a second predetermined negative potential level to the middle one of said collimating electrodes which is substantially equal to said second predetermined potential level applied to said collector electrode thereby providing a strong lens for collimating said low velocity pencil beam.

24. The method of claim 23 comprising the further step of during said second times applying a third predetermined potential level to said backing member which is slightly more positive than said second potential level applied thereto whereby said low velocity pencil beam impinges upon said storage electrode thereby selectively to erase said charge pattern thereon.

25. The method of claim 23 comprising the further steps of during said second times applying a third predetermined potential level to said backing member which is slightly more negative than said second potential level applied thereto whereby said low velocity pencil beam in passing through said apertures is modulated by said charge pattern on said storage electrode, and taking an electrical output signal from said display screen.

References Cited by the Examiner UNITED STATES PATENTS 2,943,231 6/ 1960 Boulet 3 l5l2 2,953,711 9/1960 Taubenslag 315-12 3,086,139 4/1963 Lehrer 31522 3,124,717 3/1964 King 315--12 3,175,114 3/1965 Callick 313-67 DAVID G. REDINBAUGH, Primary Examiner. T. A. GALLAGHER, Assistant Examiner. 

1. IN A DIRECT VIEWING STORAGE TUBE SYSTEM; DISPLAY SCREEN MEANS; APERTURED CHARGE STORAGE ELECTRODE MEANS HAVING A CONDUCTIVE BACKING MEMBER AND A SECONDARY EMISSIVE INSULATOR THEREON; MEANS FOR AT FIRST TIMES DIRECTING A HIGH VELOCITY PENCIL ELECTRON BEAM ONTO SAID STORAGE ELECTRODE MEANS THEREBY TO PROVIDE A CHARGE ON AN ELEMENTAL AREA THEREOF RESPONSIVE TO THE BEAM CURRENT, SAID MEANS FOR DIRECTING SAID HIGH VELOCITY BEAM INCLUDING CATHODE MEANS; MEANS FOR DIRECTING A LOW VELOCITY FLOOD BEAM OF ELECTRONS ONTO SAID STORAGE ELECTRODE MEANS WHICH PASSES THROUGH THE APERTURES THEREIN AND IS MODULATED BY THE ELEMENTAL CHARGES THEREON; MEANS APPLYING FIRST POTENTIALS TO SAID DISPLAY SCREEN MEANS, SAID BACKING MEMBER, SAID CATHODE MEANS, AND SAID FLOOD BEAM MEANS; MEANS FOR AT OTHER TIMES DIRECTING A LOW VELOCITY PENCIL BEAM ONTO SAID STORAGE ELECTRODE MEANS WHICH APPROACHES THE SAME AT SUBSTANTIALLY ZERO ENERGY, SAID MEANS FOR DI- 